This is a continuation of the ongoing project on cytogenetic monitoring with mammalian chromosomes. We plan to continue the use of mammalian cells in culture as our primary material for testing chemical mutagens, both known and unknown, but in all experiments, the S9 microsomal fraction will be used in determining if metabolic activation or inactivation of each compound exists. We also plan to use in vivo cells (mouse, chinese hamster) to test mutagen effects, especially on germline cells. We shall also explore the possibility of estimating genetic stability (or instability) of human subjects by subjecting lymphocyte cultures to a set protocol to test the degree of cytogenetic damage, because preliminary data suggest that this may be a profitable approach.